This invention relates to fireplaces, and more particularly to an air distribution system for supplying air from outside the building structure to a fire within an interior fireplace. Systems containing general provisions for supplying outside air have been known for a long time, since it has long been recognized that it is more efficient to use unheated outside air to support the fire in the fireplace than to use heated room air.
Unfortunately, however, a great number of existing fireplaces, perhaps even the majority, have been constructed without outside air supplies. This is probably due to the historical cheapness of heating fuels, at least in the United States, so that the efficiency of a fireplace was not an important consideration. In fact, the fireplace in many cases was primarily for "atmosphere" rather than heat.
However, with the passing of the era of cheap fuel, has come a rekindled interest in wood as an alternative and renewable heat source. There is also a growing recognition that existing fireplaces would greatly benefit from efficiency-improving modifications. However, since they are masonry structures, they tend to be permanent, and thus difficult and expensive to modify except in relatively superficial ways. Asthetic considerations also limit the designer's freedom, lest his modifications produce something which no longer looks like a "fireplace".
Thus, many fireplaces are now being equipped with glass doors which substantially reduce the amount of air flow up the chimney from the room. Some fireplaces have also been equipped with heat extraction units within the fireplace for circulating warm air or water from the fireplace for heating the house. However, little has been done to provide outside air for supporting the combustion. The air for the fire continues to be drawn from the room itself, usually through small ports at the base of the glass door frame. Some fireplaces have pits connected to the outside for ash collection and removal, and some homeowners have opened these for supplying air. While this improves the efficiency of the fireplace, the blast of air through the pit creates a forge effect. This generates a hot spot in the middle of the fireplace which sometimes consumes the grate along with the logs.
A need thus remains for an inexpensive yet effective fireplace air distribution system for supplying air to a fire in a masonry fireplace from outside the building structure. Such a system should be readily suited for inexpensive and convenient installation in existing fireplaces, and should supply the outside air to the fire as needed without being affected by strong winds or gusts outside the building structure nor creating hot spots within the fireplace.